Blood fractionating is quite useful since human blood is a complex mixture of red blood cells, white cells and platelets suspended in a liquid plasma. The plasma, about 55 percent by volume of the blood, is a solution of water, salts and proteins. Each of the blood fractions is useful individually and in various combinations and therefore, apparatus, systems and methods for fractionating blood are common.
Blood plasma has particular use for diagnosis and therapy, either as whole plasma or as plasma proteins. Currently, plasma is obtained from human donors by a time consuming and rather cumbersome process. A needle is inserted into a donor's vein and about 500 milliliters of blood are removed during a time span of 15 to 20 minutes. The bag containing the blood is removed and centrifuged and the supernatant plasma is removed to another container, the cells being returned thereafter to the donor. The total time required to draw the blood, produce the plasma and reinfuse the red blood cells, is about 90 minutes. The process includes several risks including the accidental return of another person's blood to the donor, an accident which may be fatal, as well as providing multiple opportunities for infection.
Various apparatus and systems have been proposed for the collection of blood plasma; however, none has proved satisfactory and none is in commercial use. Such systems are described in U.S. Pat. No. 3,705,100, issued to Blatt et al., Dec. 5, 1972, for: BLOOD FRACTIONATING PROCESS AND APPARATUS FOR CARRYING OUT SAME, and in U.S. Pat. No. 3,788,319, issued to Gillette, Jan. 29, 1974, for, SYSTEM FOR EXCHANGING BLOOD ULTRAFILTRATE. The Blatt et al. device has several disadvantages, not the least of which is the extremely slow plasma production rate. The Gillette patent discloses a device, but includes neither construction details, nor operational data.